The present invention relates to a liquid discharging apparatus and a method for discharging liquid such that a given amount of liquid is discharged.
During manufacturing processes of various technological fields such as a liquid crystal substrate manufacturing technique, a magnetic disc manufacturing technique, a multi-layer wiring board manufacturing technique, and the like in addition to a semiconductor wafer manufacturing technique, chemical liquid such as photoresist liquid, spin-on-glass liquid, polyimide resin liquid, pure water, etchant, organic solvent, or the like has been utilized. And, in order to apply these liquids, a liquid discharging apparatus has been used.
For example, in the case where the photoresist liquid is applied to a surface of a semiconductor wafer, a given amount of photoresist liquid is dripped from the liquid discharging apparatus under the condition that the semiconductor wafer is rotated in a horizontal plane. Because amounts for dripping the photoresist liquid affect thickness of a photoresist film formed by baking the photoresist liquid dripped, an accurate control is required.
Such the liquid discharging apparatus is mostly used, which has an elastically deformable pump member for forming a pump chamber as a pump for sucking and discharging liquid.
As the elastically deformable pump member, each of Japanese Patent Laid-open No. 10-47234 and No. 2000-15168 discloses one using a bellows, or Japanese Patent Laid-open No. 8-170744 discloses one using a diaphragm, or further Japanese Patent Laid-open No. 11-230048 discloses one using a flexible tube, or the like. In a liquid discharging apparatus having the pump member such as a bellows or the like, a pump chamber for being expanded and contracted by the pump member is divisionally formed therein. And, in the pump chamber, both an inflow passage communicating with a liquid storage tank and a discharge passage communicating with a discharge nozzle are connected to each other. The inflow passage and the discharge passage are provided with an inflow side valve and a discharge side valve which open and close respective passages, respectively.
The elastically deformable pump member such as a bellows or the like is driven by a drive section comprising a motor, a fluid-pressure actuator or the like, and thereby the volume of the inside of the pump chamber is changed. And, by executing a sucking step of contracting the bellows with the inflow side valve open and the discharge side valve closed and of sucking liquid into the pump chamber from the liquid storage tank, and a discharging step of extending the bellows with the inflow side valve closed and the discharge side valve open and thereby of discharging the liquid from the pump chamber, the liquid is discharged from the discharge nozzle.
Recently, in the manufacturing processes of various technical fields in addition to the semiconductor wafer manufacturing technique, high discharge accuracy has been required about the liquid discharging apparatus in order to adapt a small size and high accuracy of each product and to improve product quality.
In the liquid discharging apparatus, negative pressure depending on suction resistance and pressure depending on the difference between liquid levels of the pump chamber and the liquid storage tank, affect the pump chamber when the pump sucks the liquid. As the liquid is consumed, the pressure depending on the difference between liquid levels of the pump chamber and the liquid storage tank changes gradually. Therefore, as the liquid is consumed, pressure of the inside of the pump chamber also changes when the pump sucks the liquid. Since volume of the inside of the pump chamber comprises a pump body and an elastically deformable pump member, if the pressure of the inside of the pump chamber changes, deformed amounts of elastically deformable pump member change. As a result, the volume of inside of the pump chamber changes too.
Accordingly, amounts of liquid sucked in the pump chamber also change, so that amounts of liquid discharged are difficult to keep constant.
An object of the present invention is to eliminate affection of the discharge amounts depending on change in a liquid level of the inside of the liquid storage tank, and to improve discharge accuracy of a liquid discharging apparatus.
According to the present invention, a liquid discharging apparatus comprises: a pump body incorporating an elastically deformable pump member therein and having a pump chamber expanding and contracting by said pump member; an inflow passage provided between said pump chamber and a liquid storage tank containing liquid, and provided with such an inflow side valve as to open when said pump member executes an operation of a suction stroke; a pressure regulating passage provided between said pump chamber and a pressure regulating opening portion, and provided with such a pressure regulating valve as to open when said pump member executes a discharging operation of an exhaust stroke and to keep pressure inside said pump chamber constant; and a discharge passage provided between a discharge nozzle and said pump chamber, and provided with such a discharge side valve as to open when said pump member executes an operation of a discharge stroke. In this liquid discharge apparatus, said pressure regulating opening portion may be open to atmosphere at a position higher than liquid level of said liquid storage tank, and the pressure inside said pump chamber through said pressure regulating passage may be set to be higher than when the operation of the suction stroke is completed.
According to the present invention, a liquid discharging apparatus comprises: a pump body incorporating an elastically deformable pump member therein and having a pump chamber expanding and contracting by said pump member; an inflow passage provided between said pump chamber and a liquid storage tank containing liquid, and provided with such an inflow side valve as to open when said pump member executes an operation of a suction stroke; a pressure regulating passage provided between a pressure regulating opening portion and said pump chamber, and provided with such a pressure regulating valve as to open after the operation of the suction stroke of said pump member is completed and that sets pressure of the inside of said pump chamber to be lower than when the operation of the suction stroke is completed; and a discharge passage provided between a discharge nozzle and said pump chamber, and provided with such a discharge side valve as to open when said pump member executes an operation of a discharge stroke. In this liquid discharging apparatus, the pressure regulating opening portion may be open to atmosphere at a position lower than liquid level of said liquid storage tank.
In this liquid discharging apparatus, said pressure regulating opening portion may be practically opened downwards and maintains a reference liquid surface by forming an interface depending on surface tension of the liquid.
In this liquid discharging apparatus, said pressure regulating opening portion may be practically opened upwards.
According to the present invention, a method for discharging liquid, in which liquid inside a liquid storage tank is discharged into a discharge nozzle by a sucking operation and a discharging operation executed by an elastically deformable pump member incorporated in a pump body and forming a pump chamber, the method comprises: a sucking step of making said pump member executing an operation of a suction stroke as a condition that an inflow side valve is opened, said inflow side valve being provided in an inflow passage connecting said liquid storage tank and said pump chamber; an exhausting step of opening a pressure regulating valve and making said pump member executing a discharging operation of a predetermined exhaust stroke with pressure inside said pump chamber keeping constant, said pressure regulating valve being provided in a pressure regulating passage connecting a pressure regulating opening portion and said pump chamber; and a discharging step of opening a discharge side valve and making said pump member executing an operation of a discharge stroke, said discharge side valve being provided in a discharge passage connecting said discharge nozzle and said pump chamber.
According to the present invention, a method for discharging liquid, in which liquid inside a liquid storage tank is discharged into a discharge nozzle by a sucking operation and a discharging operation executed by an elastically deformable pump member incorporated in a pump body and forming a pump chamber, the method comprises: a sucking step of making said pump member executing an operation of a suction stroke as a condition that an inflow side valve is opened, said inflow side valve being provided in an inflow passage connecting said liquid storage tank and said pump chamber; an exhausting step of opening a pressure regulating valve and setting pressure inside the pump chamber to be lower than when the operation of the suction stroke is completed, said pressure regulating valve being provided in an pressure regulating passage connecting a pressure regulating opening portion and said pump chamber; and a discharging step of opening a discharge side valve and making said pump member executing an operation of a suction stroke, said discharge side valve being provided in a discharge passage connecting said discharge nozzle and said pump chamber.
In the present invention, since pressure inside of the pump chamber before a discharging operation becomes constant due to the pressure regulating opening portion without depending on a liquid surface level of the liquid storage tank, discharge with high precision can be achieved.